Filtered Containment Venting SystemInstalled IMI FCVS Page 20 Beznau Nuclear Power Plant – Layout for Westinghouse 2 loops PWR Shielded local control room Stack along reactor building

© 2012 CCI AG. All rights reserved.

Filtered Containment Venting System

NRC Public Meeting, September 4th 2012Rockville, MD

IMI Nuclear (CCI AG)

Denis Grob – Manager Nuclear Services Division

Page 1


Content

� Overview

� How it works

� Experimental base

� Results

� Installed Filtered Containment Venting System (FCVS)

� Sizing

� Why choosing the IMI Filter?

� Conclusions

Page 2


Overview

�The problem: The core damage scenario might require depres-surization (venting) of the containment

�The solution: A first generation of filtered containment venting system (FCVS) has been installed on approximatly 120 reactors worldwide

�A second generation of FCVS with a unique filtering efficiency hasbeen developed by CCI and is ready for implementation

�Safety authorities and utilities have expressed interest to the proposed technology

Page 3


How does it work?

Page 4

Stage 1: Nozzle Scrubber

Stage 2: Co-current Scrubber & Gas volume

Stage 3: End Separator

Water level

Nozzles

Mixing elements

Filtration & separator

Recirculation zone

The filter vessel

Contaminated gas inlet from

containment

Clean gas outlet to stack


How does it work – Stage 1, Nozzle scrubber

Vessel

Mixing elelements

Sparger assemblies

Distribution system side arms

Central distribution pipe

Riser


Drain line

Inlet pipe

How does it work – Stage 3, end separator

Triple deflectionTriple deflectionTriple deflection


How does it work – Summary

Page 7

First Stage

� Efficient scrubbing by flow injection nozzle with special baffle plates:

• disintegrating gas jet• strong turbulence for high

mass and heat transfer• distribution of gas bubbles

over whole cross section• Efficient bubble break-up

�Specified depressurization rate defined by flow limiting nozzle

�Arrest any flame propagation from containment by the water in the filter

�Excellent decontamination for mid to high flows

Second Stage

� Co-current scrubber within the core section increases mass transfer

� Large residence time through trapped bubbles in recirculation zone

� Gas volume for water level variation and suppression of droplet carry-over

� Excellent decontamination for mid to low flows

� Chemistry to scrub and fix volatile iodine species unique to 2nd

generation

Third Stage

� Droplet separator

© 2012 CCI AG. All rights reserved. Page 8

How does it work – Chemistry

Efficient retention of iodine species in an aqueous solution with two processes occurring simultaneously and starting with the operation of the system:

1. Faster reduction (decomposition to I-) of all iodine species, especially the most volatile ones, with any oxidation level entering into the solution or generated in the solution into iodide ions by simultaneous use of a reducing agent (sodium thiosulfate) and a co-agent (phase transfer catalyst)

2. Efficient retention of iodide ions generated in the aqueous solution and/or entering into the solution in form of iodine salts by suppressing the thermal and radiolytic oxidation (re-volatilization) of iodide ions by the use of the co-agent

These faster reduction and retention processes are efficient at any state of the aqueous solution; strong acidic to strong basic solutions, cold to very hot solution, and under irradiation. This allows for a long term retention of all iodines species in the filter vessel.

The combination of fast reduction AND retention of iodines(patent granted) is the unique feature of the 2nd generation FCVS


How does it work – Layout

N2N2

-

Reactor building

Containment

Inlet Basket

Rupture disk, only forpassive system option

Isolation valves

Water conditioning - immediate

Water conditioning - long term

StackClean gas line

Contaminated gas line(2 lines for BWR) Drain

Isolation valves

Not shown: Nitrogen vessel inertization if necessarybecause of H2 presence


Experimental data base

Page 10

R&D on FCVS – a short History

� CCI developed a FCVS in the 1980 time frame based on:- Extensive SULZER Experience in Filtration systems on:

� Concurrent scrubbers (mixing elements) and distillation columns � SULZER mixing and filtration elements

� An extensive development and qualification program was conducted at SULZER in the late 1980’s and the early 1990’s

� Verification tests and further qualification tests were conducted at the Paul Scherrer Institute (PSI) during 1994 to 2003

� Absolute retention of all gaseous iodine activity: Tests series with new chemistry dedicated to obtain fast and efficient destruction of volatile iodine species from 2002 to 2008


Experimental data base – Initial R&D

Page 11

Aerosol test loop used for initial development and qualification <1993

Basic Testing of filtration Elements:

• Nozzles • Co-current mixing elements • Droplet separator

Full Scale Segment Testing:

• Filter qualification and variation of mainparameters such as flow, temperature,aerosols

• Re-suspension (and clogging) of laststage

Column inlet

Column outlet


Experimental data base – Verification & further tests

Page 12

Test loop used for Further Qualifications for Aerosol Retention at PSI (1993-1995)

Plasma used to evaporate tin powder. After condensation of tin vapor, SnO2 particles are generated

A representative module of FCVS filter used for aerosol tests

Facility to prepare aerosol laden steam-gas mixture flow


Experimental data base – Iodine retention tests

Page 13

Qualification test for gaseous iodine species retention (2000 – 2002)

Iodine species generation and feed system Iodine species on-line/grab sampling measurement system

No high retention of methyl iodide and I2 obtained but finally…



Page 14

..the way to success with mastering iodine retention chemistry (2002 – 2008)

� Mastering iodine chemistry in aqueous phase to

• Obtain fast and efficient destruction of volatile iodine species to iodide ions (methyl iodide representing all high volatile organic iodide species and I2 for all other gaseous species)

• Fix iodide ions to suppress their radiolytic and thermal oxidation

� Over 1000 tests conducted using I2 and CH3I covering:

• Very acidic to strong basic solutions• Room to high solution temperature• A large range of initial CH3I concentrations• A large range of individual and coupled usage of both additives• Effect of other impurities (irradiation products, fission products, etc.)• Small to large dose • Effect of in situ �-irradiation and external �-irradiation• Static and dynamic systems• Effect of additives on the aerosol scrubbing

…with specially developed measurement techniques to follow chemical reaction products



Page 15

Influence of radiation on iodine retention

Reaction vessel in the �-irradiation chamber and

gamma-cell

Reaction vessel, apparatus for distillation and activity control systems as well as the remote control units are ready for the transfer to the hot cell for in-situ � irradiations


Experimental data base – Conclusions of the tests (I)

Page 16

� Activity retention, overall minimum decontaminationfactors (DF):

for the 2nd generation FCVS:

� Aerosols » 10‘000� Elemental iodine (I2) > 1’000� Organic iodide (CH3I) > 1’000

In the following operational conditions:• Flow rate ratio of larger than 10• Multiple venting possible – no release of fission products (desorption, re-

vaporization) because FP trapped in filter water only • Post venting – no long term release of fission products including

iodine(s) bound in filter water (re-volatilization) because of chemical binding

• No filter clogging and hot spot risk• DF valid with low pH (3), all temperatures including boiling conditions,

sub-micron to micron particle size, highest filter load

in comparison with 1st generationFCVS requirements:

> 1‘000> 100 none!


Experimental data base – Results

Droplet Separator

Impact Nozzle

Mixing Elements& Recirculation

Decontaminationshare (qualitative)


� Permanent sink for iodide ions enabling absolute iodine retention

Test data shows no free iodide ions available in the water due to effective fixation reaction by the co-agent …

…therefore, thermal and radiolytic oxidation of iodide ions to volatile I2 does not occur

� Re-volatilization of iodines does not occur

Source of iodide ions in FCVS:

- aerosols: scrubbed metallic iodides (CsI)- gaseous: scrubbed elemental iodine and organic

iodide

Experimental data base – Results


Experimental data base – Conclusion of the tests (II)

Improvements of filtration from 1st to 2nd generation

Accident�PhaseRelevant,�volatile�Nuclids

Spec.�Retainment�Factor�for�FCVS�Gen.�1

Spec.�Retainment�Factor�for�FCVS�Gen.�2

conservative best�estimate conservative best�estimate

Phase�1:�short�term�retainment�capacity�after�first�ventings�of�scrubber�

/filter�containers

Cs�134/137�aerosols Min�.1‘000 >200‘000 Min.�10‘000 >200‘000

I�131�organic 1 <5 Min.�1‘000 >1‘000

I�131�elementary 100 100 Min.�1‘000 >1‘000

I�131�aerosols� Min�.1’000 >200‘000 Min.�10‘000 >200‘000

Phase�2:�long�term�retainment�capacity�after�

several�ventings�of�scrubber�/filter�containers

NEW�CONSIDERATION!�FROM�R&D

Cs�134/137�–aerosols Min.�1‘000 >200‘000 Min.�10‘000 >200‘000

I�131�organic 1 <5 Min.�1‘000 >1‘000

I�131�elementary 1 <5 Min.�1‘000 >1‘000

I�131�aerosols 1 <5 Min.�10‘000 >200‘000


Installed IMI FCVS

Page 20

Beznau Nuclear Power Plant – Layout for Westinghouse 2 loops PWR

Shielded local control room

Stack along reactor building

Separate building

Filter boundariesFlow 4.3kg/sec, Pressure 4.6 bar


Installed FCVS – Beznau Nuclear Power Plant

Page 21

Local control room with manual control valves and instrumentation


Layout for General Electric BWR6

Installed FCVS – Leibstadt Nuclear Power Plant

2 Filter vessels without separate buildingClean gas line Filter boundaries:

Flow: 13.8kg/sec, Pressure 3.6 bar

Shielded Control Room


Delivery of two filter vessels to the NPP Leibstadt



Cardan shaft for valves actuation

Passive line with rupture disk

active line with 2 isolation valvesActive line with 2 isolation valves



Manual / electricalactuators

Instrumentation



�Specified by Customer:

• Filtration: Required min. decontamination factors (DF) for aerosols,elementary iodine and organic iodine and boundary conditions accordingly,e.g. flow, gas composition, temp., pressures, cycling, aerosols size andconcentration etc. Required Filtration behavior for mid and long term (re-volatilization, re-vaporization, re-suspension)

• Thermodynamics: Max. vent flow rate at given containment pressure, containment volume, gas composition in containment at venting initiation, total decay heat of aerosol and iodine to be scrubbed, steam and non condensable gas generation rates after venting initiation, reactor decay heat evolution at venting initiation and afterwards*

• Fission product: Total aerosol (active/inactive) mass to be scrubbed, total iodine species (metallic, elemental iodine and organic iodide) to be scrubbed, time frame for about the full activity to be scrubbed, acidification potential

• Operation: Time without any operator intervention (autarky), passivity without power, full passivity without power and rupture disk venting opening

• Layout (walkdown mandatory): Control room, filter room, penetration, existing in-and outlet piping

Note: Mandatory for quote

Sizing


�Specified by Customer:

• Filtration: Required min. decontamination factors (DF) for aerosols,elementary iodine and organic iodine and boundary conditions accordingly,e.g. flow, gas composition, temp., pressures, cycling, aerosols size andconcentration etc.

• Thermodynamics: Max. vent flow rate at given containment pressure, containment volume, gas composition in containment at venting initiation, total decay heat of aerosol and iodine to be scrubbed, steam and non condensable gas generation rates after venting initiation, reactor decay heat evolution at venting initiation and afterwards*

• Fission product: Total aerosol (active/inactive) mass to be scrubbed, total iodine species (metallic, elemental iodine and organic iodide) to be scrubbed, time frame for about the full activity to be scrubbed, acidification potential

• Operation: Time without any operator intervention (autarky), passivity without power, full passivity without power and rupture disk venting opening

• Layout (walkdown mandatory): Control room, filter room, penetration, existing in-and outlet piping

Note: Mandatory for quote

Sizing


� Given in CCI test base: Specific test results (aerosols, iodines) with variation of nozzles sizes, pressure ratios and volumetric flows in the 1 nozzle-full scale test bench:

• 1.6 to 5 bar (1.5 to about 4 pressure ratio) filter inlet pressure• Subcooled to saturated pools, pure steam to non-condensable gas to

steam mixture flows• Submicron (0.3 �m to 2.5 �m –geometric-) particles, different

materials for aerosols • Very small to very high iodine concentrations for iodine retention

(iodine concentration, absorbed dose)• Iodine removal at low (pH 2) to high (pH14) pH and cold to hot water

temperature• Complementary test data base: Iodine and aerosol pool scrubbing

and aerosol removal in water pools with submerged structures, droplet entrainment by bubble burst

Sizing


�Calculated by CCI:

• Select orifice size and number to match desired max. vent flow rate and simultaneously check the filter pressure ratio for the lowest flow with regard to decontamination

• Check Depressurization behaviour

• Determine Vessel size

– Desired autarky (consider simultaneously: steam condensation, water evaporation, water drainage back to filter)

– Allocate space for aerosol mass remaining below sparger area (no return of contaminants in the containment necessary)

– Remain in the experimental data base for iodine retention (Iodine concentration, absorbed dose)

• Filter hydrogen concentration calc. and decision on mitigation

Sizing


�Designed by CCI:

• P & ID

• Layout draft including control and filter rooms, piping inlet and outlet lines, penetration

• Fittings and instrumentation

• Installation – Operation - Maintenance

• Shielding

• ....

Sizing


Why choosing the IMI filter?Available filtering technologies:

• Impact Nozzle• Chemistry• Mixing elements• Recirculation zone

• Metal fiber filter• Molecular sieve

• Venturi Nozzle• Chemistry• Metal fiber filter

• Venturi Nozzle• Chemistry• Metal fiber filter• Molecular sieve


Why choosing the IMI filter? – Critical issues

Narrow volumetric flow range leads to low

depressurization rate (long depressurization time) and thus hinders fast operation of low pressure injection

pumps

Outlet throttling leads to high vessel pressure = high energy - H2 risk!

Sharp drop indecontamination

factors of Venturies (20!) when out of

narrow flow range and filter water level

causes large aerosol tansport to metal fiber

filtration stage

Venturi Nozzle:



Decay heat of fission products leads to re-

vaporization ofaerosols (hot spots)

Metal fiber filter:

High risk of cloggingwith high aerosol load and high temperature

Corrosion and high temp. damage to

metal fibers

Multiple venting leads to re-suspension of

deposited fission products



Multiple venting leads to re-entrainment of fission

products

Molecular Sieve:

Poisoning of zeolite through halogens, sulfur compounds,

acid fumes and other fission products

Pre-heating with active N2 gas and pre-conditioning

with H2

High temperature sharply reduces absorption, i.e. by

steam absorption and catalytic H2-O2 / silver

reaction

High tempearture by Decay heat

(includingabsorbed nobles gases) leads to

Re-vaporizationof aerosols and

iodine


Why choosing the IMI filter? – Summary Critical Issues� Venturi nozzles have a narrow flow range decontamination efficiency an thus

allow the transfer of the filtration function to the next filtration stages (fine mesh stage, molecular sieve)

� The Venturi nozzles and Dry filter technologies (fine mesh, molecular sieve) do not allow for fast depressurization rate (or sudden pressurization) due to flow limitation

� Metal fiber filter have a high clogging risk with uncontrollable (radioactive)materials and liquid/solid particules mixtures

� Molecular sieve need pre-heating and pre – conditioning. They are subject to uncontrollable poisoning

� Dry only Filtering technologies solution, i.e. fine mesh or/and molecular sieve, have to cope with the the total amount of fission product heat: re-vaporization and filter damage is expected

� The ACE tests late eightys are from today’s view not representative for high aerosol load, large flow range and irradiation influence on filtration. The re-volatilization, re-vaporization and re-suspension are not adressed


Why choosing the IMI filter? – The reasons are:

� Highest decontamination factors for aerosols from high to low flows allows wide operation flexibility, e.g. fast depressurization without compromise on filtration

� Highest decontamination factors for iodines by adequate chemistry

� Re-volatilization of iodines – issue solved under all possible conditions by adequate chemistry

� Re-vaporization of aerosols and iodines - issue solved, i.e. allfission products kept in filter water. The same reason excludes Re-entrainment when multiple venting cycles venting

� Best laboratory worldwide ready to answer specific Utilities request ready to test


Conclusions

Page 37

� IMI - PSI have developed a 2nd generation of Filtered Containment Venting System with a unique, highly efficient filter system

� For the first time in the nuclear power industry, a technology to prevent the release of active aerosols AND iodines species to the environment is available

� The installed approximately 120 FCVS, mainly in Europe have deficiencies in filtering aerosols and iodines. Other reactors worldwide do not have any filtering capabilities despite the fact that approximately half of the core damages scenarios might require containment venting

�Nuclear Safety Athorities and Utilities may consider the installation of a 2nd generation Filtered Containment Venting System to better protect public health and safety and preclude the possibility of land contamination due to the recent events


Disclaimer

The information presented here is not considered to be a commercial evaluation and or interpretation of performances of the available containment venting filter systems.

The receiving organization/person is alone responsible for the use of the information presented for any application if the use causes any damage in any kind. IMI/CCI reserves all rights thereto.


Documents

Filtered Containment Venting SystemInstalled IMI FCVS Page 20 Beznau Nuclear Power Plant – Layout for Westinghouse 2 loops PWR Shielded local control room Stack along reactor building